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- Farahbakhshazad, Neda
(författare)
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A constructed vertical macrophyte system for the retention of nitrogen in agricultural runoff
- 2000
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Ingår i: Environmental technology. - : Informa UK Limited. - 0959-3330 .- 1479-487X. ; 21:2, s. 217-223
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Tidskriftsartikel (refereegranskat)abstract
- Recent evidence for the importance of luxury rhizome accumulation of N by the common reed Phragmites australis opens the possibility for N retention in constructed vertical wetlands. The removal of nutrients (N and P) from agricultural runoff was investigated in columns planted with P. australis in a sand bed. Nitrate demonstrated a Linear removal with detention time (60-300 min) and was accounted for by membrane-Limited root uptake. Ammonia was effectively removed from agricultural runoff, with nitrate removed at longer detention times. Detention time based on a targeted nitrate removal therefore represents a suitable design parameter for a vertical macrophyte system. On the other hand, ammonia was more effectively removed at low concentrations, but ineffectively removed at higher concentrations. Nitrogen is effectively accumulated in rhizomes which could be mechanically ground, composted and returned to agriculture.
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| 2. |
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| 3. |
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| 4. |
- Norin, Malin, 1967, et al.
(författare)
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Leaching of organic contaminants from storage of reclaimed asphalt pavement
- 2004
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Ingår i: Environmental Technology (United Kingdom). - : Informa UK Limited. - 1479-487X .- 0959-3330. ; 25:3, s. 323-340
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Tidskriftsartikel (refereegranskat)abstract
- Recycling of asphalt has been promoted by rapid increases in both the use and price of petroleum‐based bitumen. Semi‐volatile organic compounds in leachates from reclaimed asphalt pavement, measured in field samples and in laboratory column test, were analysed through a GC/MS screen‐test methodology. Sixteen PAH (polyaromatic hydrocarbons) were also analysed in leachates from the column study. The highest concentrations of semi‐volatile compounds, ‐ 400 μg 1‐1, were measured in field samples from the scarified stockpile. Naphthalene, butylated hydroxytoluene (BHT) and dibutyl phthalate (DBP) were the most dominant of the identified semi‐volatiles. The occurrence of these compounds in urban groundwater, also indicate high emission rates and persistent structures of the compounds, making them potentially hazardous. Car exhausts, rubber tires and the asphalt material itself are all probable emission sources, determined from the organic contaminants released from the stockpiles. The major leaching mechanism indicated was dissolution of organic contaminants from the surface of the asphalt gravels. In the laboratory column test, the release of high‐molecular weight and more toxic PAH was higher in the leachates after two years than at the commencement of storage. The concentrations of semi‐volatiles in leachates, were also several times lower than those from the field stockpile. These results demonstrate the need to follow up laboratory column test with real field measurements.
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| 6. |
- Jantsch, Tor Gunnar, et al.
(författare)
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A simple spectrophotometric method based on pH-indications for monitoring partial and total alkalinity in anaerobic processes
- 2003
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Ingår i: Environmental Technology. - 1479-487X. ; 24:9, s. 1061-1067
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Tidskriftsartikel (refereegranskat)abstract
- Partial alkalinity, as a measure of bicarbonate concentration, and total alkalinity, as a measure of the concentration of bicarbonate and volatile fatty acids, are useful parameters for monitoring anaerobic digestion processes. This paper reports a new method based on pH-indicators and spectrophotometric measurements for the monitoring of partial and total alkalinity. The method was used in an off-line procedure for monitoring of an anaerobic process and displayed less than 5% deviation from the traditional method of measuring partial and total alkalinity, as well as being rapid and reproducible. A flow injection analysis system based on the method was used on-line for monitoring overload in a UASB reactor, which demonstrated changes in alkalinity not easily registered using traditional methods.
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| 7. |
- Magnusson, R, et al.
(författare)
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Determination of chemical composition and mutagenicity in particles from chainsaw exhaust. Experimental set-up, stability and results from two different fuels
- 2000
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Ingår i: Environmental Technology. - 0959-3330. ; 21:7, s. 819-29
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Tidskriftsartikel (refereegranskat)abstract
- A dilution tunnel for sampling of particles and gaseous emissions in chainsaw exhaust was constructed and tested for reproducibility. In addition the equipment was used to measure chainsaw emissions when using two different fuels, aliphatic petrol with synthetic lubricating oil and regular lead-free petrol with mineral lubricating oil. The content of polycyclic aromatic hydrocarbons (PAH) and the mutagenicity of sampled particles were measured as well as the concentration of carbon monoxide (CO), nitrogen oxides (NOx) and aldehydes in the exhaust. particles were sampled isokinetically and collected on a filter followed by two polyurethane foam plugs (PUF) in series for sampling of the semivolatile components. PAH were analysed by a coupled liquid chromatography - gas chromatography (LC-GC) system and mutagenicity testing was carried out by using Ames Salmonella assay. The measured physical parameters as well as the particulate, semivolatile and gaseous emissions showed that reproducible measurements of exhaust emissions could be achieved using this experimental set-up. In terms of mutagenicity when testing for reproducibility, a small but significant effect was observed for the Salmonella strains TA98 and TA100 in the absence of a metabolizing system, both for the particulate phase and the semivolatile components. A significant difference was seen between the two different fuels tested, the conventional petrol with mineral oil having 5-10 times higher concentrations of different PAH compounds and a much higher mutagenic effect for all strains. This difference was seen both for the particulate phase and the semivolatile components.
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| 8. |
- Mshandete, Anthony, et al.
(författare)
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Influence of recirculation flow rate on the performance of anaerobic packed-bed bioreactors treating potato-waste leachate
- 2004
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Ingår i: Environmental Technology. - 1479-487X. ; 25:8, s. 929-936
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Tidskriftsartikel (refereegranskat)abstract
- The performance of anaerobic, packed-bed bioreactors treating leachate from potato waste was evaluated in terms of organic loading rate (OLR) as well as the recirculation flow rate. Two 1 litre bioreactors, filled with porous glass beads as biofilm carriers and with continuous recirculation flow rates of 10 ml min(-1) and 20 ml min(-1) respectively, were used in the experiment. The OLR applied to each bioreactor was increased stepwise from 4 to 12 kg chemical oxygen demand (COD) m(-3)d(-1) by increasing feed flow rate. The methane yields decreased with increasing OLR in both bioreactors. The methane yield for the bioreactor with the lower recirculation flow rate ranged between 0.10 and 0.14 m(3) CH4 kg COD-1 removed, while for the other bioreactor it was 0.14-0.20 m(3) CH4 kg COD-1 removed. Both bioreactors demonstrated stable COD removal which was around 95% for the bioreactor with lower flow of recirculation while for the other it was 92%, over a range of OLRs of 4-8 kg COD m(-3)d(-1). The bioreactor with the lower recirculation flow rate showed operational stability when a high OLR, namely 12 kg COD m(-3)d(-1), was applied, while the other one became overloaded. There was an accumulation of volatile fatty acids which gave a corresponding drop in pH because the system had a low buffering capacity and this thus ultimately led to process failure. This study demonstrated the suitability of a packed bed bioreactor operated at lower recirculation flow rate for treating leachate from potato waste.
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| 9. |
- Möller, Anna, et al.
(författare)
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Precipitation of heavy metals from landfill leachates by microbially-produced sulphide
- 2004
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Ingår i: Environmental Technology. - 1479-487X. ; 25:1, s. 69-77
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Tidskriftsartikel (refereegranskat)abstract
- Four leachates from two landfills in Sweden were treated for the removal of heavy metals with the aid of sulphate-reducing bacteria (SRB). Both continuous and batch experiments were performed. A packed-bed process was used for sulphide production. The metals studied were As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn. The continuous experiments showed that Cd and Cu were most efficiently removed and that Cr was the most difficult to precipitate. In a continuous experiment with one of the leachates, the removal of Cd, Cu and Zn depended upon the retention time in the system. In the batch experiments, precipitation of the metals was a relatively fast process. No significant differences in metal concentrations were found between experiments terminated after a day and those terminated after a week. In a batch experiment involving one of the leachates, the precipitation of Cd and Cu was shown to be dependent upon the metal:sulphide ratio. Removal of the metals increased with an increase in the sulphide:metal ratio up to 45:1. The process with SRB showed an interesting potential for removal of heavy metals from leachates. One of the two leachates for which the highest metal removals were obtained came from a landfill for hazardous waste.
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| 10. |
- Schuur, JHB, et al.
(författare)
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Separation of coal-tar constituents from soil particles in a two-liquid-phase slurry system
- 2003
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Ingår i: Environmental Technology. - 1479-487X. ; 24:6, s. 755-765
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Tidskriftsartikel (refereegranskat)abstract
- An evaluation has been made of the capability of rapeseed oil to dissolve polycyclic aromatic hydrocarbon (PAH) crystals in a biphasic system and of its capability to extract PAHs from polluted soil in a two-liquid-phase (TLP) slurry system. Up to 220 g l(-1) of the crystalline hydrocarbons could be dissolved in the organic phase, indicating oil/water-partitioning coefficients of 10(5). When soil from a former gasworks site was treated in a TLP slurry system, it was found that a certain critical amount of vegetable oil had to be added in order to form a free oil phase. Single and multiple extractions gave similar results for multiple short-term and single long-term treatments, with a maximum of 87% for pyrene release. Following a 30-day bioslurry treatment, the total concentration of the 16 EPA PAHs in the soil decreased from 2740 mg kg(-1) to 1366 mg kg(-1). This was followed by one of three different 12-day post-bioslurry treatments. Further bioslurry treatment reduced the final concentration to 1002 mg kg(-1). Abiotic treatment with a surfactant (Brij 30) achieved a reduction to 797 mg kg(-1). Treatment with rapeseed oil gave the best reduction to 343 mg kg(-1).
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